Notes: Spacecraft is currently listed in "100 (or so) brightest special-interest satellites" at NORAD. Updates of those data on this web site will be available frequently. Archived data of satellites. Updates of those data on this web site will be available not frequently but by opportunity.» With some satellite you find a link to the mission description at the NSSDC.
Each row of a single update contains the date the data is valid. You find also the last update date of the related file.